...Crumpled newspaper and crumpled brown wrapping paper is the ultimate solution. It doesn't shift, it compresses nicely and it's very resilient. It's what the commercial shipping companies use.
The companies with the volume and funding use two-part urethane foam bags top and bottom, giving a conformal packaging. One such eBay seller is SunnKing, from whom I've bought a few items that were packed in that way (one of which was an SGI Indigo2 IMPACT (purple) system). Two-part urethane foam (sold in cans as 'Great Stuff' TM among other brands) isn't cheap packaging, but I know of at least one factory which packages fragile but heavy lower-volume items (such as high-intensity discharge lighting systems and lamps for same) using this technology. The machine fills and makes the bags in one step from two continuous sheet rolls and two tanks. Higher volume luminaires and lamps get custom molded styrofoam packaging. But for a system with the chassis weight of a TRS-80 Model II/12 -series (including 16, 16B, and 6000) such foam is probably too dense, and the chassic might still destroy the case, especially the screw bosses. You don't want rigid packaging.
EMC's factory packaging is the ultimate, though, and is a different foam product (LDPE I believe is the base for it) that is 100% recyclable and is made from a high percentage recycled LDPE product. Although for their hard drives, which have an MSRP in the $2,500 range each, they package five or ten to the box using an HDPE clamshell arrangement, with the drive in a clear HDPE carrier. Very light, but custom molded, and 100% recyclable. The clamshells are pretty flimsy, and rather similar to Maxtor's packaging back in the day, but much thinner. This flimsiness actually helps, and it greatly reduces the shock transfer from the box to the product.
I personally like the elastomer sheet suspension systems that Amazon and others use, but they're not for really heavy items. A shock cord mount system, like used in road cases for high-end PA systems, would be sweet, but they are very expensive for shipping purposes.
For a quality packing job for something with this fragile of plastic (like, say, an SGI O2), disassembling all of the plastic off of the system and shipping it in a separate box from the heavy chassis is wise. Even if properly packed, a fully assembled O2 is likely to destroy its own case in shipping, as the case plastic is incredibly fragile these days (this is one of the primary reasons I've not tried to sell either of my two O2's, as I know the buyer is not likely to want to pay for what I will do to pack it properly, and I'm not willing to take the risk of a return for a shattered case). Or you need packaging with substantial give to it; the crumpled paper works as well as it does because it has give to it, but it's somewhat unpredictable in how consistently it gives.
